Improvements in &amp; relating to pile and post driving equipment

ABSTRACT

The present invention is directed to an impact driver, which relies on multiple connected piston and cylinder assemblies which sequentially fire; a first auxiliary piston assembly charged to compress a compressible fluid with a piston rapidly releases the charge on said piston allowing the compressed fluid, which is typically a gas, to accelerate said auxiliary piston. This auxiliary piston is connected to a second travelling primaty piston assembly which it accelerates. Within the primary piston assembly a primary piston can be charged to compress a compressible fluid. The charge on the primary piston can also be rapidly released to accelerate the primary piston. The primary piston may be connected to a striking element, or successive travelling piston and cylinder assemblies which ultimately connect to a striking element.

FIELD OF INVENTION

The present invention is directed to apparatus such as used for driving posts and piles into the ground, and typically where the post or pile is impacted. It can also be used for other impact driving applications such as rock breaking, mining, etc.

BACKGROUND DESCRIPTION

The present invention is directed to impact and post drivers, though it should be appreciated that they may find other applications.

Typical impact type pile drivers use a falling weight to impact the top of a post or pile. The degree of impact is dependent upon the mass and velocity (typically the distance by which the weight falls) of the impacting weight, and in simple terms this roughly equates to F=½ mv², though the mathematics, in reality, is a little more complex. However it is enough to illustrate that increasing the height which the weight falls (increasing the velocity) has an exponential increase in the resulting applied force, as opposed to the linear increase in force resulting from increasing mass.

In practice, pile drivers are limited in both their height and mass able to be lifted. The consequence is that as heavy a mass as can be lifted (and supported) reasonably is used, but as high a height (drop) as possible is used. Hence, most pile and post drivers are large, bulky, and tall machines and often have to be disassembled, or require special consideration, for transport. This does limit their use, which commonly where the expense and difficulty of getting the pile driver to the site is justified—such as on large building projects.

The diesel hammer utilises a falling weight compressing air and igniting injected diesel fuel to help drive an impact head against the pile as well as driving the weight back up and drawing in fresh air for a new cycle (falling/ignition/driving/lifting the weight). Such devices are relatively efficient once running, but are noisy and largely continuous. Also, unlike drop hammers, the height of a drop and frequency of driving cannot be controlled during the course of driving in diesel hammers. This can cause problems in certain ground formations, such as where there is underlying layers of minerals or bedrocks. It has been reported that the use of a diesel hammer in such situations can cause damage to the piles when it hits the more compacted layers. It was necessary to vary the parameters of driving in order to address this problem, which is beyond the scope of diesel hammers.

Also, the prior art devices are largely limited to driving piles vertically. In some instances it is desirable to drive posts or piles at an angle—such as a fence or strainer post on a descending ridgeline or slope, where the posts are perpendicular to the fence wires which are in turn parallel to the contour of the hill. The prior art devices are not typically suitable for such applications, even if able to be transported and stabilised in such a situation.

In summary, it would be very useful to have pile and impact driving equipment which allows driving parameters to be altered readily. This can include driving frequency, and impact force.

It would also be very useful to have apparatus which is more compact and transportable than the prior art and able to be used in a wider range of applications, and mounted on a wider range of vehicles—such as typical farm tractors, small utility trucks, trailers, etc. It would be useful if such apparatus could be used where it is often impractical to use large prior art equipment—such as in remote or awkward areas, and tight spaces. Examples can include everything from house piles to fence posts (including in remote hilly areas), up to full size industrial and construction applications.

Accordingly there is a need for improved apparatus able to be more versatile, compact, and useable than typical large prior art equipment such as falling weight and diesel hammer drivers.

Accordingly, it is an object of the present invention to consider the above problems and propose an alternative.

At the very least it is an object of the present invention to provide the public with a useful alternative choice.

Aspects of the present invention will be described by way of example only and with reference to the ensuing description.

GENERAL DESCRIPTION OF THE INVENTION

According to one aspect of the present invention there is provided impact driving equipment in which there is provided an outer cylinder housing a primary internal cylinder assembly also acting as a weight, and wherein this primary internal cylinder includes an internal primary piston in turn connected to a striker plate;

the primary internal cylinder assembly being connected to an auxiliary piston within a further auxiliary piston and cylinder assembly, and in which sliding of the auxiliary piston therein is linked to movement of the primary internal cylinder assembly within the outer cylinder;

and wherein there is a fluid reservoir area on one side of the auxiliary piston in said auxiliary piston and cylinder assembly which, when fluid is introduced, pushes said piston against gas which begins to increase in pressure;

and wherein introducing fluid into said fluid reservoir area also introduces fluid to within said primary internal cylinder assembly, thereby pushing the primary internal piston against pressurized gas therein;

and wherein the pressure of said introduced fluid can be rapidly released to allow the pressurized gas to act against said pistons and consequentially drive the striker plate in a striking action.

According to a further aspect of the present invention there is provided impact driving apparatus comprising an auxiliary piston assembly comprising an auxiliary piston and cylinder, and in which one side of the auxiliary piston can be charged to pressurise a compressible fluid on the other side thereof;

said auxiliary piston being connected to a primary piston assembly in turn comprising at least a primary piston and associated cylinder assembly; said primary piston being able to be charged to pressurise a compressible fluid on the other side thereof; and wherein

said primary piston assembly is able to slide within an outer housing;

said primary piston being connected to a striking element for delivering energy to a target.

According to another aspect of the present invention there is provided impact driving apparatus, substantially as described above, in which charging a piston comprises introducing hydraulic fluid into a reservoir bounded at least partly by a said piston and its associated cylinder.

According to another aspect of the present invention there is provided impact driving apparatus, substantially as described above, in which the charge on a piston can be rapidly released.

According to another aspect of the present invention there is provided impact driving apparatus, substantially as described above, in which hydraulic fluid can be released through a port having a relatively large effective cross-sectional area.

According to another aspect of the present invention there is provided impact driving apparatus, substantially as described above, in which a said port comprises a seated valve under bias towards a closed position.

According to another aspect of the present invention there is provided impact driving apparatus, substantially as described above, in which the charge on the auxiliary piston is released prior to the charge on the primary piston.

According to another aspect of the present invention there is provided impact driving apparatus, substantially as described above, in which the charge on the primary piston is released after its associated cylinder assembly has acquired velocity due to the release of the charge on the auxiliary piston.

According to another aspect of the present invention there is provided impact driving apparatus, substantially as described above, in which the parameters for timing of charge release, extent of pressurisation of compressible fluid, and component masses, are selected so that recoil on the travelling primary piston assembly after release of the charge on the primary piston causes said primary piston assembly to any one of slow, stop, and change direction.

According to another aspect of the present invention there is provided impact driving apparatus, substantially as described above, which includes means for slowing the striker element after it has travelled a predetermined distance.

According to another aspect of the present invention there is provided impact driving apparatus, substantially as described above, which comprises preventing further rapid release of hydraulic fluid acting on the primary piston.

According to another aspect of the present invention there is provided impact driving apparatus, substantially as described above, in which the compressible fluid is a gas.

According to another aspect of the present invention there is provided impact driving apparatus, substantially as described above, in which the gas is nitrogen, or an inert gas mixture.

According to another aspect of the present invention there is provided impact driving apparatus, substantially as described above, in which the striker element allows different heads to be attached or substituted.

According to another aspect of the present invention there is provided impact driving apparatus, substantially as described above, including mounting means for a vehicle.

There are a number of possible variations of embodiments of the present invention, and which may have differing features according to user need. These are envisaged as being within the scope of the present invention.

To assist the reader it is probably best to explain the principles of the invention in simple terms and to elaborate from there. This will greatly simplify understanding the invention.

In simple terms one could state that the present invention relies on two piston assemblies interconnected in series to drive a striker plate, or the like, for impacting an object—such as a post or spike to be driven into the ground, rock face, wall, etc., or for other applications such as rock breaking, battering rams, etc.

In the preferred embodiments of the present invention, the serial arrangement of piston assemblies potentially allow for an accumulation of kinetic energy which is delivered ultimately via the striker plate. The potentially realisable advantages include being able to build a much more compact unit, when compared with the traditional prior art, for delivering a specific amount of energy. This then makes the device easier to transport, and to mount on smaller and more manoeuvrable vehicles.

Elaborating on the preferred embodiments, we have a auxiliary piston arrangement, characterised by the fact that it is able to be charged to pressurise a compressible fluid, typically a gas. The method of charging the piston against the compressible fluid is optional, but hydraulic arrangements are preferred in the preferred embodiments.

Another characteristic is to be able to release the pressure or force acting on the piston (to compress the compressible fluid) relatively quickly so that the piston can be driven and accelerated quite quickly by the compressed fluid.

Coupled to the piston is a primary piston assembly including cylinder and piston. This primary piston assembly also acts as a mass, being effectively a driven weight accelerated by the release of the auxiliary piston.

The primary piston assembly is also characterised by its piston, i.e. the primary piston in the apparatus, being able to be charged to compress a compressible fluid, typically also a gas. Also, the charge causing the compression of the compressible fluid must also be able to be released relatively quickly. Again, the preferred method of charging the piston is hydraulically.

In practice the charge acting on the primary piston is released after the primary piston assembly has begun accelerating. While the primary piston could be attached to a third piston assembly (ad infinitum), in the preferred embodiment it is connected to the striker plate.

The striker plate, prior to release of the charge acting on the primary piston, already has kinetic energy by virtue of the associated mass (the primary piston assembly) to which it is connected, and the fact that this mass already has velocity due to the firing of the auxiliary piston assembly.

Releasing the charge on the primary piston, then allows the compressible fluid in the assembly to accelerate the primary piston and striker plate. We therefore have the rapid release of more ‘stored energy’ which is converted to kinetic energy.

We have the sequential release of stored energy acting on masses, which eventually is transferred to a target via the striker plate. By storing energy through the compression of a compressible fluid, we can store much more potential energy than can be obtained by having a mass falling the equivalent distance as the height of the compressed fluid chamber. We are effectively converting stored energy into kinetic energy, rather than relying on gravity, and this results in a more efficient use of space—allowing not only for a much more compact unit to be built, but also for it to be used on an angle, including horizontally or inverted; thereby opening up many more applications for the invention.

By sequential energy release, and utilising the mass of the primary piston assembly as an accelerated weight, we can harness much more stored energy—two charges instead of one. As these combine to accelerate the striker plate, we can achieve a much higher velocity at the striker plate than a falling weight in a compact unit. Since E_(k)=½ mv², velocity is the greater contributor to energy than mass, which also means we can use less mass and produce a lighter unit.

According to Newton's third law of motion, there is an equal and opposite reaction on the accelerated mass of the primary piston assembly as the primary piston fires. This results in a recoil action. If the primary piston assembly was stationary when the primary piston fired, then this may drive the remainder of the primary piston assembly in the opposite direction by a distance ‘x’. This distance would need to be accommodated into the design of the apparatus. However, by firing the primary piston when the primary piston assembly is moving, the recoil energy must first stop the remainder of the primary piston assembly before it can move it in the opposite direction. Hence the recoil distance is less than ‘x’. This allows the designer to produce a unit which is more compact. Also, it helps prevent the moving primary piston assembly from slamming into the opposite end of the apparatus as it is slowed, or even reversed, according to the precise parameters of timing, geometries, pressurisation, mass, etc. which skilled reader may incorporate into a specific design of an embodiment of the present invention—there is a degree of user choice, and flexibility of design here to allow a user to optimise the design of their specific embodiment.

Hence, most of the energy can be delivered to the striker plate, from a compact unit which is lighter and smaller than traditional falling weight apparatus.

The nature of the invention will be more clearly seen from the following illustrations, which are given by way of example only.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-sectional drawing illustrating one preferred embodiment of the invention, and

FIG. 2 is a schematic cross-sectional drawing illustrating the embodiment of FIG. 1 and also illustrating fluid connections.

DESCRIPTION OF PREFERRED EMBODIMENT

With reference to the drawings, and by way of example only, we have a piston (J) able to slide with a cylinder (JJ). This open ended cylinder is open to a reservoir area (JT) filled with nitrogen (or other) gas and sealed off by a seal or piston (X).

Underneath the piston (J) is a fluid (typically hydraulic fluid) reservoir (H) in communication (not shown) via a non-return valve with another fluid reservoir (B) under floating piston (D). The non-return valve allows fluid to travel from (H) to (B) but not from (B) to (H).

In operation, and preparing for a strike (impact), hydraulic fluid is introduced from (H) to (B). This then pushes piston (D) upwardly acting against nitrogen (or other) gas within reservoir (DT).

Reservoir area (B) is also open to the reservoir area (A) underneath a floating valve (G), which seats (VS) against the inside contours of middle cylinder (MC), by means of a further conduit (not shown) incorporating a flow restrictor.

As valve (G) has a larger surface area exposed to fluid in reservoir (A) than the surface area exposed to reservoir (B), and there is also a bias spring (F) pushing it (G) closed against seat (VS), the fluid in reservoir (B) cannot push valve (G) open.

By pushing oil from (H) to (B) and (A) the result is that piston (D) pushes against the nitrogen gas in (DT). Typically the uncompressed pressure may be around 50-300 Barr, and compressed around 80 to 400 Barr.

By pushing oil into reservoir area (H) we not only force oil into (B) and (A) but also start forcing piston (J) upwardly towards reservoir area (JT). Piston (J) is connected by rod (L) to the middle cylinder (MC) which also acts as a floating weight. The gas in reservoir (JT) may be equalized to that within the outer cylinder reservoir volume (OR) by virtue of floating piston (X) and which typically converts (OR) into a large accumulator area. The pressure within (JT) is typically around 10-20 Barr but may be increased to 50-70 Barr, which is typically sufficient to support the weight of everything connected to piston (J) should the device be used on an angle or even inverted.

Hence, in preparation for striking we have introduced fluid into reservoir volume (H) which raises piston (J) against the gas in the reservoir volume (JT). This also pulls cylinder (MC) and associated components with it, and also introduces fluid into reservoir (B), and also into (A) via a conduit with a flow restrictor, thereby closing valve (G) against its seat (VS). This then results in piston (D) being forced upwardly against the pressurized reservoir (DT).

In turn, piston (D) is connected by rod (M) to striker plate (N), and thus also raises it.

Next we shall describe the striking sequence. Ideally the volume (H) is not too big so that oil can be released rapidly via a release conduit (not shown).

As the pressure from reservoir (H) is released, pressure from within reservoir (JT) then pushes piston (J) down rapidly along with all the connected components.

The non-return valve between reservoir (H) and reservoir (B) prevents fluid from returning from (B) to (H) when the pressure from reservoir (H) is released. Thus the pressure in reservoir (B) does not alter.

As the middle cylinder (and weight) (MC) travels downs towards gland (S), poppet valve(s) (R) strike the gland (S) and releases pressure from within reservoir area (A).

As reservoir (B) is connected to (A) by a restricted conduit, it can only slowly replenish reservoir (A). Accordingly the pressure differential ((B) is higher than (A)) then pushes valve (G) open and opens the valve at the seat (VS). This then rapidly releases oil from reservoir from (B) into the lower pressure of the outer casing area. The large opening at the valve seat is able to release oil faster than a typical conduit porting into the reservoir are. Consequently there is a very rapid release of any pressure acting on the underside of piston (D) and thus the pressurized gas within reservoir (DT) very quickly accelerates piston (D), and its associated components (including striker plate (N)), downwardly and so that it ultimately hits sliding plate (T) resting on top the pile or post (POST).

However, in this preferred embodiment, we do get some recoil from the pressure of nitrogen against weight (MC) as piston (D) is accelerated downwardly, thereby slowing weight (K) so it doesn't slam into gland (S). This can result in the capture of more energy as this energy is transferred to striker plate (N) rather than being wasted on cylinder/weight (MC) impacting gland (S). Also as the tapered base (DB) of piston (B) starts to overlap with in restricted cylinder portion (U) we also get reduced flow from reservoir volume (B) which slows piston (D) and provides some hydraulic cushioning before it strikes internal components within the cylinder (MC).

FIG. 2 illustrates in standard schematic form the main hydraulic fluid connections including pump connection (PM), tank connection (TK), restrictor valve (RV) and non-return valve (NRV).

For simplicity, the various conduits, for supplying and controlling hydraulic fluid according to the above description, have not been shown though it will be anticipated that a skilled addressee of the art will be able to readily implement these.

This specification is also based on the understanding of the inventor regarding the prior art. The prior art description should not be regarded as being authoritative disclosure on the true state of the prior art but rather as referencing considerations brought to the mind and attention of the inventor when developing this invention.

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the spirit or scope of the present invention as described herein.

It should also be understood that the term “comprise” where used herein is not to be considered to be used in a limiting sense. Accordingly, ‘comprise’ does not represent nor define an exclusive set of items, but includes the possibility of other components and items being added to the list. 

1-15. (canceled)
 16. Impact driving apparatus comprising an auxiliary piston assembly comprising an auxiliary piston and cylinder, and in which one side of the auxiliary piston can be charged to pressurise a compressible fluid on the other side thereof; said auxiliary piston being connected to a primary piston assembly in turn comprising at least a primary piston and associated cylinder assembly; said primary piston being able to be charged to pressurise a compressible fluid on the other side thereof; and wherein said primary piston assembly is able to slide within an outer housing; said primary piston being connected to a striking element for delivering energy to a target.
 17. Impact driving apparatus as claimed in claim 16 in which charging a piston comprises introducing hydraulic fluid into a reservoir bounded at least partly by a said piston and its associated cylinder.
 18. Impact driving apparatus as claimed in claim 16 in which the charge on a piston can be rapidly released.
 19. Impact driving apparatus as claimed in claim 18, in which hydraulic fluid can be released through a port having a relatively large effective cross-sectional area.
 20. Impact driving apparatus as claimed in claim 19 in which a said port comprises a seated valve under bias towards a closed position.
 21. Impact driving apparatus as claimed in claim 16 in which the charge on the auxiliary piston is released prior to the charge on the primary piston.
 22. Impact driving apparatus as claimed in claim 16 in which the charge on the primary piston is released after its associated cylinder assembly has acquired velocity due to the release of the charge on the auxiliary piston.
 23. Impact driving apparatus as claimed in claim 16 in which the parameters for timing of charge release, extent of pressurisation of compressible fluid, and component masses, are selected so that recoil on the travelling primary piston assembly after release of the charge on the primary piston causes said primary piston assembly to any one of slow, stop, and change direction.
 24. Impact driving apparatus as claimed in claim 17 which includes means for slowing the striker element after it has travelled a predetermined distance.
 25. Impact driving apparatus as claimed in claim 24 which comprises preventing further rapid release of hydraulic fluid acting on the primary piston.
 26. Impact driving apparatus as claimed in claim 16 in which the compressible fluid is a gas.
 27. Impact driving apparatus as claimed in claim 26 in which the gas is nitrogen, or an inert gas mixture.
 28. Impact driving apparatus as claimed in claim 16 in which the striker element allows different heads to be attached or substituted.
 29. Impact driving apparatus as claimed in claim 16 including mounting means for a vehicle. 